1. Field of the Invention
The present invention relates to a radio frame control device, a radio communication device, and a radio frame control method.
Priority is claimed on Japanese Patent Application No. 2008-288622, filed Nov. 11, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, “LTE (Long Term Evolution)” has been known, for example, as one of the 3GPP (Third Generation Partnership Project) standards as a next-generation mobile communication scheme to realize high-speed, broadband radio communication (for example, see 3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA): Physical channels and modulation”). The LTE uses OFDMA (Orthogonal Frequency Division Multiple Access) as a downlink radio transmission scheme (link from a base station to a terminal station). The OFDMA scheme is a multicarrier transmission scheme for performing communication using a broadband signal configured from a plurality of subcarriers of which frequencies are orthogonal to each other, and realizes multiple access between one base station and a plurality of users using a different subcarrier for every user (terminal station).
FIG. 8 is a diagram showing a configuration example of a downlink radio frame of the OFDMA scheme. A radio frame shown in FIG. 8 is based on the LTE. In FIG. 8, one radio frame is configured from a plurality of subframes. One subframe is configured from two slots. As shown in FIG. 9, one slot has a configuration in which resource blocks (RBs) are connected in a frequency direction. For example, when a subcarrier interval is 15 kHz, one RB may be configured by either “12 Subcarriers in Frequency Direction×7 OFDMA Symbols in Time Direction” or “12 Subcarriers in Frequency Direction×6 OFDMA Symbols in Time Direction”. In the OFDMA scheme, the arrangement information indicating an RB where a packet destined for each user is arranged within a subframe is determined for every subframe. A transmitter of the base station determines a radio resource to be used to transmit a downlink packet according to the arrangement information. A receiver of each terminal station receives a packet for a local station within a subframe according to the arrangement information.
In the LTE, four allocation types 0, 1, 2 (localized), and 2 (distributed) are defined as a method of allocating RBs to a terminal station in a subframe (for example, see 3GPP TS 36.213, “Evolved Universal Terrestrial Radio Access (E-UTRA): Physical channels and modulation”). Different restrictions are provided in the allocation types. When RBs are allocated to the terminal station, they must be allocated to the terminal station under the restrictions according to any one of the allocation types. Now, each allocation type will be described briefly.
[Allocation Type 0]
In the allocation type 0, RBs are allocated to a terminal station in a unit of a resource block group (RBG). The resource block group is configured from a plurality of RBs continuous on a frequency axis. In the example of FIG. 10, the RBG is configured from three continuous RBs on the frequency axis, and the RBs are allocated to the terminal station in the RBG unit.
[Allocation Type 1]
In the allocation type 1, RBs are allocated to the terminal station in an RB unit for the same subset. In the example of FIG. 11, three subsets (the number of subsets is the same as the RBG size) are provided and the RBs are allocated to the same terminal station in the RB unit for the same subset. In each subset, the RBs are sequentially arranged in the RBG unit.
[Allocation Type 2 (Localized)]
In the allocation type 2 (localized), RBs are allocated to a terminal station in the RB unit on a logical frequency axis. In this regard, all RBs allocated to the same terminal station need to be continuous on the frequency axis. As illustrated in FIG. 12, mapping is performed on a physical frequency axis to be exactly the same as the logical frequency axis. According to the allocation type 2 (localized), only the start and end points of RB allocation may be represented on the logical frequency axis and the amount of RB allocation information to be reported to the terminal station may be reduced.
[Allocation Type 2 (distributed)]
In the allocation type 2 (distributed), RBs are allocated to a terminal station in the RB unit on the logical frequency axis. In this regard, all RBs allocated to the same terminal station need to be continuous on the frequency axis. As illustrated in FIG. 13, mapping is made in a predetermined pattern on the physical frequency axis.